An essential requirement for film holders for radiographic purposes consists in that the film proper and its intensifying foils must hug each other closely and be maintained strictly planar.
Conventional film holders for the purpose in hand include two complementary box-like portions which are connected together by a hinge and include a lining of foam rubber, or the like substance. The aforementioned lining engages the intensifying foil and presses the latter against the X-ray film proper. Film holders of this description are subject to several drawbacks. There is no assurance that the pressure exerted by the foam rubber or like lining is sufficiently uniform over the entire areas of films and foils. Moreover, linings of foam substances are subject to ageing, i.e. their resiliency and thickness are subject to change, and thus sooner or later lose their ability to function as intended.
The above drawback of film holders having foam rubber or the like linings or backings was conducive to the development of vacuum film holders.
In an attempt to avoid some of the many troubles encountered with vacuum film holders for radiographic applications, film holders have been designed which are substantially in the form of a plastic hose. A film sandwiched between a pair of intensifying foils is inserted into such a hose-type film holder, whereupon the latter is evacuated. One problem arising out of the use of such film holders consists in that the hose must be sealed upon evacuation thereof which, in the instant case, is a time consuming step. The use of hose-type film holders is also expensive because they can only be used once, and then must be discarded.
It is the principal object of the invention to provide vacuum film holders for radiography which are not subject to the drawbacks and limitations of prior art film holders, and more particularly the prior art film holders which have been described above.